I have seen this somewhere else, I loathed it. This only works when you have a small community where everyone knows everyone, not a large one where you have thousands of people where many of them of regularly change their names. Above all the potential abuse far outweighs any kind of usefulness this idea has. I got continuously tagged for whatever reason and it annoyed the hell out of me; I simply find this concept in fact extremely rude as it's almost like people are breathing into your face. You can force countless of people to the threads you want way too easy. There is no merit in that and considering that it's so easy to abuse, I say no.
You can even receive infractions if you start spamming people's profiles with links to threads if they are annoyed by it. This system pretty much does exactly the same, only far easier and on a much larger scale.
You also take the fun out of browsing the forums when people start dictating where you should be. People would start using this to get people to their threads, so imagine when many people start doing it and then I'm still talking about normal members, not trolls. Those could simply write your name in every post they make.
Barely any - I don't even see any - positive sides and easily abused, so I'm against it. And whether we decide this democratically or not is likewise decided by us, so in the end we are the ones who decide. Seriously is now already too difficult to browse a forum?